More than 20% of children in parts of Ethiopia's Somali region of Ogaden are acutely malnourished, a report warns.
Aid agencies have been sounding the alarm for months
Ethiopia's Disaster Prevention and Preparedness Agency says the situation is critical and humanitarian assistance is needed to prevent an emergency.
Recent rebel attacks and army counter insurgency operations, combined with poor rains over the past two years, have disrupted food supplies.
In August, the UN said emergency food aid was needed for 600,000 people.
This latest report, prepared with technical assistance from the aid agency Save the Children, is the first attempt to measure the effects of the current situation on young children in the Ogaden.
It follows reports submitted to the government last month by both Medecins sans Frontieres (MSF) and the UN, which also sounded the alarm.
The Ethiopian government had promised to ensure that the food and medical needs of the people in the region were met in collaboration with UN agencies and other partners.
Ogaden suffered badly in 2000 following drought
But by the time the children were assessed in early September more than 20% of under fives were already found to be acutely malnourished and 1.5% severely acutely malnourished - a term which indicates the kind of listless children with wasted arms and legs found in famine situations.
This, the report says, indicates a critical nutritional status situation, which is something short of a humanitarian emergency but could very quickly turn into one without immediate action.
The BBC's Elizabeth Blunt in the capital, Addis Ababa, says the report scrupulously avoids allotting blame but shows how natural and man-made causes have combined to put these children in danger.
Rains and rebels
The area of Fiq where the assessment teams carried out their work was already impoverished and short of food even before the upsurge in rebel attacks this year and the army operation which followed.
The Ethiopian army has been accused by Ogaden National Liberation Front (ONLF) separatists of operating a food blockade and causing a man-made famine.
The rains in Fiq have been poor for the past two years and there is little pasture for the animals.
Now security operations have disrupted normal commercial food supplies and made men in particular afraid to travel to places where they might be able to buy.
Prices of grain have doubled, while the price of livestock - people's main source of income - has halved.
Even those with money, the report says, have no easy access to food and an urgent response is needed to ensure that the children in these areas survive.
In early September MSF warned that a disaster was looming in the region and complained it had been denied access by the government in Addis Ababa.
Later the same month a UN fact-finding mission found a "pervasive climate of fear" in Ogaden and called for an independent investigation into abuses of civilians.
The ONLF was founded in 1984 and is fighting for independence from Ethiopia, complaining of discrimination by the central government against the region's Somali-speaking nomads.